Direct-Sequence Spread Spectrum with DPSK Modulation and Diversity for Indoor Wireless Communications

Direct-sequence spread spectrum with differential phase shift-keying (DPSK) modulation and code-division multiple-access is a promising approach for wireless communications in an indoor environment, which is characterized in this paper by a Rayleigh-fading multipath channel. In this study, we consider two specific channel models having different path-delay distributions and average path power profiles. A star configuration, in which each user exercises average power control in transmitting to a central station, is the basic communication unit, which could be one cell in a cellular hierarchy. We obtain the performance of a single link between a user and its receiver in the central station, and consider two types of diversity, selection diversity and predetection combining to exploit the multipath. A similar system with coherent PSK (CPSK) modulation has been studied previously for one of the channel models considered here. For the same channel model, we show that the irreducible error probability with selection diversity is about half an order of magnitude higher when DPSK is used instead of CPSK. With predetection combining, the performance improves significantly in comparison with selection diversity as the diversity order increases. DPSK modulation with predetection combining is akin to coherent PSK with optimal maximal-ratio combining, but is simpler to implement. The performance with selection diversity for a second channel model, which is based on measurements in an office building, is not significantly different. This indicates that the spreadspectrum approach is rather robust to the path-delay distribution and average path-power profile.     

一种基于超再生原理的直扩通信系统新型接收机的设计

在短距离窄带无线通信系统中,具有结构简单、低成本、低功耗和灵敏度较高(相对于再生接收机)等优点的超再生接收机已经有几十年的应用历史。这里,根据超再生的基本原理,构建出一种用于对直序列扩频(DS-SS)信号进行非相干检测的扩频接收机的新型结构,并对其在2.4GHz的ISM波段的宽带应用进行分析。     

Performance of Quadrature Amplitude Modulation for Indoor Radio Communications

The performance ofM-QAM for indoor radio communications is evaluated via a realistic model for indoor multipath propagation [1]. It is found that the outage (BER < 10^-4) is about 0.3 percent at 1 Mbit/s and 20 percent at 4 Mbits/s. Two-antenna predetection diversity reduces the outage from 1.2 to 0.04 percent at 2 Mbits/s. Increasing the signaling pulse rolloff factor from 0.5 to 1.0 reduces the outage by not more than 35 percent.     

四种级联差分相位调制码的100 Gbit/s传输

在级联相位调制的100 Gbit/s光信号传输系统中,对差分相移键控非归零码(NRZ-DPSK)、差分相移键控归零码(RZ-DPSK)、差分四相相移键控非归零码(NRZ-DQPSK)和差分四相相移键控归零码(RZ-DQPSK)进行了比较研究.当四种信号通过90 km的标准单模光纤(SMF)和16 km的色散补偿光纤(DCF)传输后,在满足相同入纤功率的条件下,NRZ-DQPSK信号具有最高的色散容限;如果仪仪考虑一阶偏振模色散(PMD),RZ-DQPSK信号具有最优的抗偏振模色散特性;当入纤功率在O～10 dBm的范围内凋节时,RZ-DPSK信号具有最好的非线性容忍度;最后比较了四种相位调制码型传输后通过不同带宽的三阶高斯滤波器后的接收性能,得出滤波器带宽值大于125 GHz后,NRZ-DPSK信号的接收性能最佳.     

Differential Phase-Shift Keying Performance on L-Band Aeronautical Satellite Channels: Test Results and a Coding Evaluation

The problem of communicating binary information from ground to aircraft viaL-band aeronautical satellite channels is addressed, with particular attention given to the effect of and means of combating diffuse-scattered multipath interference. Differential phase-shift keying (DPSK) is considered throughout. Test results of a recent flight-test program are summarized and compared to theory for uncoded DPSK. We then discuss and evaluate the use of diffuse convolutional codes in conjunction with threshold decoding to improve error probability on the fading channel. Simulation has shown that a power saving of 8 dB may be gained at 10^-5error rate for typical channel conditions with very little complexity.     

Reconfigurable All-Optical Logic Gates for Multi-Input Differential Phase-Shift Keying Signals: Design and Experiments

Differential phase-shift keying (DPSK) signals are promising candidate for the long-haul transmission systems. However, the development of the all-optical signal processing techniques for the DPSK signals is still in its infancy, especially the all-optical logic operations. In this work, a general scheme for reconfigurable logic gates for multi-input DPSK signals with integration possibility is proposed. Benefiting from the optical logic minterms developed by two kinds of optical devices, i.e., optical delay interferometers and semiconductor optical amplifiers (SOAs), target logic functions can be realized by combining specific minterms together. The scheme is reconfigured by changing the phase control of the delay interferometers or the input wavelengths. The latter approach was adopted in the experimental trials. Although the outputs of the scheme are on-off keying (OOK) signals, the data format is compatible with all-optical decision circuits where OOK format is preferred. Two- and three-input experiments are carried out at 20 Gbit/s with nonreturn-to-zero DPSK signals. Various logic operations are demonstrated, including full sets of two- and three-input minterms, AND, NOR, XOR, and XNOR logic operations where the AND and NOR logic are derived simultaneously and the XOR and XNOR logic are convertible. The optical SNR as well as the Q-factor of the two- and three-input results are measured and compared. It shows that the input powers to the SOAs are critical in achieving good extinction ratio and the Q-factor of logic results degrades when several minterms are combined. The recovery time of the SOAs need to be optimized as well. Finally, the scaling issues of the scheme are discussed.     

Radio Signals with Large Relative Bandwidth for Over-the-Horizon Radar and Spread-Spectrum Communications

It is known that radio signals must have a small relative frequency bandwidth if structures and circuits resonating with sinusoidal functions are to be used for radiation and reception. This paper develops concepts showing that a small relative frequency bandwidth is also required for the use of amplitude or frequency modulation of sinusoidal radio carriers in the usual form. However, it is easy to modify the usual methods of amplitude and frequency modulation for signals with large relative frequency bandwidth. The primary application of such methods is for over-the-horizon radar and spread-spectrum communications in the short-wave region where the desired relative frequency bandwidths are neither small (in the order of 0.01 or less) nor close to 1.     

Design and Analysis of a Wavelet Packet Modulation Based Differential Chaos Shift Keying Communication System

Wireless Personal Communications - In this paper, a new multicarrier based DCSK system that is combined a wavelet packet modulation (WPM) with differential chaos shift keying (DCSK) and named...     

Coding and Modulation Techniques for Frequency-Hopped Spread-Spectrum Communications Over a Pulse-Burst Jammed Rayleigh Fading Channel

In this paper, the results of comparing the performance of various forward error correction techniques and several modulation formats when used over a nonselective Rayleigh fading channel in the presence of a pulse-burst jammer are presented. Both binary and nonbinary codes are considered, as well as concatenated codes consisting of either a block or a convolutional inner code and a Reed-Solomon outer code. Finally, the use of side information to allow the decoding of both erasures and errors is also analyzed.     

Improving a Hybrid Method of Indoor Propagation Modeling for Wireless Communications Systems

1　IntroductionThewirelesscommunicationsystemshavebeendevelopedrapidlyintherecentyears.Ithasnotonlycalledresearchers’attentiontomodelingtechniquesinInternet[1 ] ,butalsomoreandmorepeopleen gagedin propagationmodelingforindoorwirelesscommunications.Theeffectivedesign ,assessmentandinstallationofaradionetworkinanindoorenvi ronmentrequireanaccuratecharacterizationoftheradiopropagationchannel.Raytracingisapopularmethodforthepredictionofradiochannelcharacter isticsofwirelesscommunicationsystems.R…     

Generalized Tamed Frequency Modulation and Its Application for Mobile Radio Communications

Continued investigation of tamed FM (TFM) has led to an extension called generalized tamed FM (GTFM). The very narrow spectral property of a GTFM signal meets the stringent requirements on bandwidth utilization in modern mobile radio applications. The principle of GTFM is first described. It is then shown that the generation of GTFM signals can be made very simple by the use of an ROM table-lookup technique. By an appropriate choice of parameters in GTFM signal generation at the transmitter, a joint optimization for coherent and noncoherent detection with regard to BER performance in the presence of additive white Gaussian noise can be achieved. For mobile radio applications, the robustness of the detection scheme to fast fading is important. A low-complexity noncoherent receiver is presented, Comprising a frequency discriminator and a simple maximum-likelihood sequence estimator. This receiver performs well in a fast fading environment. Computer simulated results of BER performance of this scheme are given. These results are confirmed by experimental measurements.     

An Upper Bound Analysis for Coherent Phase-Shift Keying with Cochannel, Adjacent-Channel, and Intersymbol Interference

An error-probability upper-bound is developed for coherent phase-shift keying (CPSK) considering the combined effects of Gaussian noise, intersymbol interference (ISI), and several peak-limited circular-symmetric (CS) components such as adjacent-channel interference (ACI) and cochannel interference (CCI). In an earlier paper [1], an upper bound was introduced, based on the "maximizing probability density function" concept, for CPSK with Gaussian noise and a single CS interference. The natural extension of this type of bound to multiple mixed interferences-such as are encountered in practice-is given in this sequel. This multiple interferer bound, which is computationally simple to use, requires only the peak and mean-square values of the several interferences involved, and is optimal in the sense that no other bound, based solely on the same information, will be lower than it. Through examples we draw comparisons with previously available results, which show that the multiple-interference limited-peak bound, when applied to composite interference situations, can be an effective tool for system design and analysis.     

Design,Analysis, and DSP-Based Implementation of a Code-Phase-Shift Keying Receiver for Wireless Local Area Network Applications

This paper introduces code-phase-shift keying(CPSK), a novel M-ary direct-sequence spread-spectrum(DS-SS) signaling technique that is particularlysuitable for wireless local area network applications. In CPSK, each of the M signaling waveforms isobtained by a different code phase shift of a singlepseudonoise (PN) sequence. It increases the data ratewithout sacrificing spreading gain, and is more power efficient over additive white Gaussian noise(AWGN) than conventional DS-SS signaling methods. Thedesign, analysis, and implementation of a DSP-basedreceiver is presented to demonstrate the practicality of the signaling method. In our design, thereceived IF signal is downconverted into two quadraturebaseband components that are filtered and A/D convertedat 1 MHz into 8-bit samples for processing by three TMS320C40 processors. The tracking andacquisition schemes are adapted from conventional DS-SSreceivers, while the carrier-wave synchronizationproblem is solved by a novel technique calledphase-invariant reception. The design is tested in AWGN andsingle-tone interference environments. Implementationlosses and acquisition performances arequantified.     

Fast Differential Unitary Space-Time Modulation Decoding for a MIMO Radio Channel

Improved decoding efficiency is achieved for differential unitaryspace-time modulation across a multiple-input multiple-output(MIMO) channel. The group nature of constellations used for signaltransmission, and hence a minimised search space for maximumlikelihood (ML) decoding are utilised to give this improvement. Aprocedure using lattice reduction for fast decoding across amultiple-input single-output (MISO) channel is generalised to aMIMO channel effectively, as a modification to a previousproposal, and used to generate the ML decoder search space.Further insight into the application of this algorithm is given.The decoding technique developed is shown to have very good errorperformance for reasonably sized MIMO channels.     

Decision Feedback Channel and Symbol Estimation Methods for CDMA Systems in Indoor Wireless Communications

A dispersive finite impulse response (FIR) channel model is often considered for indoor wireless channels. For the FIR channel model in this paper, we consider the joint estimation of channel parameters and data symbols in indoor code division multiple access (CDMA) systems. The least squares formulation is constructed for the joint estimation incorporating the decision feedback technique. This formulation is suitable for indoor CDMA systems that usually have a small processing gain. The formulation is further modified to provide a recursive approach to estimate the channel vector.     

An Upper Bound on the Error Probability for Differential Phase-Shift Keying in the Presence of Additive Gaussian White Noise and Peak-Limited Interference

A new upper bound on the error probability for differential phase-shift keyed transmission in the presence of additive Gaussian white noise (AGWN) and peak-limited interference is estimated using numerical techniques. An error probability expression is evaluated for various interference angles and the maximum value found is chosen as the upper bound. A simple approximation is presented and found to be close to the upper bound. This upper bound is shown to be a realistic bound, hence it could be useful for practical design purposes.     

Precoder Design and Impulsive Noise Mitigation Scheme for Industrial Wireless Communications

In industrial wireless scenarios,the impulsive noise(IN)incurred by machine running or operation causes a serious influence on the powerlimited industrial wireless communications.It is challenging to ensure efficient and reliable transmission with quality of service(QoS)guarantee for machinetype communication devices(MTCDs).Considering the IN in the industrial process,this paper establishes the multiuser multiple-input single-output(MU-MISO)orthogonal frequency division multiplexing(OFDM)system model,which combines transmitter and receiver design.Two precoding schemes are designed to improve communication effectiveness at the transmitter.More specifically,the precoder design scheme which combines semi-definite relaxation(SDR)with difference-of-two-convex-function(D.C.)iterative algorithm,is developed by utilizing the Dinkelbach method to improve the system effectiveness.To decrease the computational complexity,we devise the quadratic-based fractional programming(QFP)algorithm,which decouples the variables by using a quadratic transform method.On this basis,the IN mitigation scheme is studied to reduce the system error rate(SER)at the receiver.With the goal of improving the reliability of industrial wireless communications,we propose a hybrid nonlinear IN mitigation(HNINM)scheme and then derive its closed-form expression of SER.The simulation results show that the proposed QFP algorithm achieves superior performance while the HNINM scheme decreases the SER of industrial wireless communications.     

RF-MEMS for Wireless Communications [Topics in Design and Implementation]

This article presents an introduction and overview of MEMS technology with a focus on RF applications of MEMS in the design of cellular handsets. A novel, integrated, high-Q tunable digital capacitor is discussed to demonstrate how RF-MEMS technology can be utilized to make high frequency components whose RF characteristics can be adjusted during operation, allowing for the first time reconfiguration of radio hardware under software control. It is concluded that as the consumer wireless market continues to grow and evolve, product designers will remain under ever increasing pressure to develop smaller, lighter, thinner products that are more functional, energy-efficient, and intuitive, and to do so faster and at lower cost. Although issues and challenges persist, opportunities abound, and RF-MEMS technology holds the promise of being a key enabler of future generations of more highly converged, cognitive, and flexible consumer wireless products.     

无线传感执行器网络双射频通信节点设计与实现

针对无线传感器执行器网络拓扑结构动态变化、通信量大、实时性强及协同工作等特点,同时为降低通信时的信号干扰,设计并实现了一种基于IEEE 802.15.4的双射频多信道通信节点。对关键的天线电路进行了分析和设计;开发了通信模块与控制决策中心的USART接口程序和双通信芯片间的I2C接口程序。